General procedure for the synthesis of 4-(4-bromophenyl)butyric acid from 3-(4-bromobenzoyl)propionic acid: zinc powder (13.0 g, 200 mmol) was stirred with mercuric chloride (1.00 g, 4.80 mmol) in water (10 mL) and concentrated hydrochloric acid (0.6 mL) for 5 min. After decanting the liquid, toluene (20 mL), concentrated hydrochloric acid (20 mL) and water (8 mL) were added sequentially. 3-(4-Bromobenzoyl)propionic acid (2.55 g, 10.5 mmol) was added to the reaction system and heated at reflux at 100 °C for 24 h, during which concentrated hydrochloric acid (1 mL) was replenished every 6 hours. After completion of the reaction, it was cooled to room temperature, filtered, and the solvent was removed from the organic phase to give a clarified liquid, which precipitated as white crystals upon cooling. The product was purified by silica gel column chromatography (eluent: ethyl acetate/hexane, 1:3, v/v) to afford 4-(4-bromophenyl)butanoic acid (2.33 g, 9.63 mmol, 91.4% yield). Mass spectrometry (ESI-quadrupole) m/z: calculated values of C10H11BrO2[M-H]-: 241.99, 243.99; measured values: 244.0 (10%), 243.0 (98%), 242.0 (11%), 241.0 (100%) (negative ion mode). High performance liquid chromatography (HPLC) retention time: 27.7 min. 1H NMR (300 MHz, CDCl3) δ (ppm): 7.40 (2H, d, J = 8.4 Hz, ArH), 7.06 (2H, d, J = 8.4 Hz, ArH), 2.63 (2H, t, J = 7.8 Hz, CH2), 2.36 (2H, t, J = 7.2 Hz, CH2), 1.97 (2H, dt, J = 7.2, 7.8 Hz, CH2), OH was not observed.
